Abstract:

An aircraft fuel tank system is disclosed in which a vent tank is provided
with an ullage vent for use in combination with an eternal flamer barrier
means during a refuelling process.

Claims:

1. An aircraft fuel tank system comprising:a vent tank comprising an
ullage vent means and an inlet from one or more fuel tanks;a vent pipe
arranged to provide fluid communication between the ullage of said vent
tank and said ullage vent means;flame barrier means operable between a
closed state in which said flame barrier means is arranged as a barrier
to flame fronts entering said vent tank via said vent pipe and an open
state in which said flame barrier means is arranged so as to enable fluid
flow between said ullage and said ullage vent means to bypass said flame
barrier means;coupling means arranged for sealingly externally coupling
an external flame barrier means to said ullage vent so as to provide
fluid communication between said vent pipe and atmosphere via a coupled
external flame barrier means; andactuator means arranged to operate said
flame barrier means into said open state in response to the coupling of
an external flame barrier means via said coupling means, said actuator
means being further operable to operate said flame barrier means into
said closed state in response to the decoupling of said external flame
barrier means from said coupling means.

2. An aircraft fuel tank system according to claim 1 in which said
actuator means is at least partially manually operable by the coupling
movement of an external flame barrier means with said coupling means.

3. An aircraft fuel tank system according to claim 1 in which said
actuator means is at least partially powered.

4. An aircraft fuel tank system according to claim 1 in which said
actuator means comprises first locking means arranged to prevent removal
of an external flame barrier means from said coupling means until said
flame barrier means is returned to said closed state.

5. An aircraft fuel tank system according to claim 1 in which said
actuator means comprises second locking means arranged to lock said flame
barrier means in said closed state, said second lock being operable to
release said flame barrier means in response to the engagement of an
external flame barrier means with said coupling means.

6. An aircraft fuel tank system according to claim 1 in which said flame
barrier means is arranged to rotate at least partially within said vent
pipe so as to switch between said open and closed states.

7. An aircraft fuel tank system according to claim 1 in which said flame
barrier means is arranged to translate to a position at least partially
outside said vent pipe general cross-section so as to switch between said
closed to said open state.

8. An aircraft fuel tank system according to claim 1 in which said flame
barrier means is positioned substantially outside the general
cross-section of said vent pipe in said open state.

9. An aircraft fuel tank system according to claim 1 in which said flame
barrier means is positioned substantially inside the general
cross-section of said vent pipe in said open state.

10. An aircraft fuel tank system according to claim 1 in which said vent
pipe comprises a first section having a cross-section sealingly
conforming to said flame barrier means in said closed state and a second
section having a larger cross section than said flame barrier means so
that translation of said flame barrier means to an open state positioned
within said second section so as to enable said fluid flow between said
ullage and said ullage vent means to bypass said flame barrier means.

11. An aircraft fuel tank system according to claim 1 in which said flame
barrier means comprises one or more valved bypass conduits operable to
enable said fluid flow between said ullage and said ullage vent means to
bypass said flame barrier means.

12. An aircraft fuel tank system according to claim 1 in which said flame
barrier means is biased into said closed state.

13. An aircraft fuel tank system according to claim 1 further comprising
one or more seals positioned between said flame barrier means in said
closed state and said vent pipe.

14. An aircraft fuel tank system according to claim 1 further comprising
one or more seats positioned within said vent pipe for seating said flame
barrier means in said closed state.

15. An external flame barrier means for use with the aircraft fuel tank
system of any preceding claim, said external flame barrier means
comprising:a hollow body member comprising a first port providing
coupling means for sealing engagement with said coupling means of said
aircraft fuel tank system and a second port providing a vent to
atmosphere; andflame barrier means arranged within said body member so as
to provide a barrier to ingress past said first port of a flame front
external to said external flame barrier means and to enable egress of
liquid fuel from said first port to atmosphere.

Description:

FIELD OF INVENTION

[0001]The present invention relates to an aircraft fuel tank system.

BACKGROUND OF THE INVENTION

[0002]Fuel tank systems for aircraft commonly comprise one or more fuel
tanks and a vent tank. The vent tank may also be referred to as a surge
tank. The vent tank is arranged to provide venting means to vent the fuel
tanks to atmosphere. Vent tanks are arranged to allow air to flow from
atmosphere into the fuel tanks as they are drained and to allow air, fuel
vapour or inerting gasses or a mixture of these to flow out of the tanks
to atmosphere as the tanks are filled. In addition, during such fill or
drain operations, vent tanks are also commonly required to equalize
pressures in normal operation due to ambient pressure changes.

[0003]Vent tanks are commonly arranged with a predetermined liquid fuel
storage capacity. This capacity provides storage for liquid fuel forced
from the fuel tanks and vent system into the vent tank, for example, as a
result of an aircraft manoeuvre or overfilling of the fuel tanks during
refuelling of the aircraft. While vent tanks are commonly arranged with
means for returning such surges of fuel to the fuel tanks in a controlled
manner, if the liquid fuel capacity of the vent tank is exceeded the fuel
is vented to atmosphere.

[0004]One problem with such surges of liquid fuel is that they may be at a
relatively high pressure during filling. If such pressure is not properly
vented then the fuel tank system may be physically damaged. This is a
particular problem if the fuel tank system comprises an integral part of
the aircraft structure. The problem may be exacerbated when fuel is cold
and thus more viscous and therefore more resistant to flow through the
venting system.

[0005]Another problem exists in that fuel storage space in an aircraft is
limited and valuable. Vent tanks may be located in areas that are not
suitable for fuel storage and generally need to be as space efficient as
possible while providing the required vent capacity. For example, vent
tanks are commonly located in the wing tips of an aircraft where space,
particularly depth, is restricted.

SUMMARY OF THE INVENTION

[0006]In accordance with an embodiment of the invention there is provided
an aircraft fuel tank system comprising:

a vent tank comprising an ullage vent means and an inlet from one or more
fuel tanks;a vent pipe arranged to provide fluid communication between
the ullage of the vent tank and the ullage vent means;flame barrier means
operable between a closed state in which the flame barrier means is
arranged as a barrier to flame fronts entering the vent tank via the vent
pipe and an open state in which the flame barrier means is arranged so as
to enable fluid flow between the ullage and the ullage vent means to
bypass the flame barrier means;coupling means arranged for sealingly
externally coupling an external flame barrier means to the ullage vent so
as to provide fluid communication between the vent pipe and atmosphere
via a coupled external flame barrier means; andactuator means arranged to
operate the flame barrier means into the open state in response to the
coupling of an external flame barrier means via the coupling means, the
actuator means being further operable to operate the flame barrier means
into the closed state in response to the decoupling of the external flame
barrier means from the coupling means.

[0007]The actuator means may be at least partially manually operable by
the coupling movement of an external flame barrier means with the
coupling means. The actuator means may be at least partially powered. The
actuator means may comprises first locking means arranged to prevent
removal of an external flame barrier means from the coupling means until
the flame barrier means is returned to the closed state. The actuator
means may comprise second locking means arranged to lock the flame
barrier means in the closed state, the second lock being operable to
release the flame barrier means in response to the engagement of an
external flame barrier means with the coupling means. The flame barrier
means may be arranged to rotate at least partially within the vent pipe
so as to switch between the open and closed states. The flame) barrier
means is arranged to translate to a position at least partially outside
the vent pipe general cross-section so as to switch between the closed to
the open state.

[0008]The flame barrier means may be positioned substantially outside the
general cross-section of the vent pipe in the open state. The flame
barrier means may be positioned substantially inside the general
cross-section of the vent pipe in the open state. The vent pipe may
comprise a first section having a cross-section sealingly conforming to
the flame barrier means in the closed state and a second section having a
larger cross section than the flame barrier means so that translation of
the flame barrier means to an open state positioned within the second
section so as to enable the fluid flow between the ullage and the ullage
vent means to bypass the flame barrier means. The flame barrier means
comprises one or more valved bypass conduits operable to enable the fluid
flow between the ullage and the ullage vent means to bypass the flame
barrier means. The flame barrier means may be biased into the closed
state. One or more seals may be positioned between the flame barrier
means in the closed state and the vent pipe. One or more seats may be
positioned within the vent pipe for seating the flame barrier means in
the closed state.

[0009]Another embodiment provides an external flame barrier means for use
with the aircraft fuel tank system of any preceding claim, the external
flame barrier means comprising:

a hollow body member comprising a first port providing coupling means for
sealing engagement with the coupling means of the aircraft fuel tank
system and a second port providing a vent to atmosphere; andflame barrier
means arranged within the body member so as to provide a barrier to
ingress past the first port of a flame front external to the external
flame barrier means and to enable egress of liquid fuel from the first
port to atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]Embodiments of the invention will now be described, by way of
example only, with reference to the accompanying drawings in which:

[0011]FIG. 1 is a schematic front view of an aircraft;

[0012]FIG. 2 is a cross-sectional front view of a vent tank in the fuel
tank system of the aircraft of FIG. 1;

[0013]FIG. 3 is a schematic cross-sectional view of the vent pipe in the
vent tank of FIG. 2 in combination with an external flame barrier means;

[0014]FIG. 4 is a flow chart illustrating the processing performed by an
actuator control system in the vent pipe of FIG. 2; and

[0015]FIGS. 5 & 6 are schematic cross-sectional views of the vent pipes in
accordance with further embodiments for use in a vent tank in combination
with an external flame barrier means.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0016]With reference to FIG. 1, an aircraft 101 comprises a pair of wings
102 faired into a fuselage 103. Each wing 102 carries an engine 104 and
part of an internally located fuel tank system 105. The fuel tank system
105 provides fuel to the engines 104. The fuel tank system comprises a
set of fuel tanks 106 and two vent tanks 107 each built-in to a
respective wing 102. The vent tanks 107 are each located towards the tip
of their respective wings 102. The vent tanks 107 are arranged to perform
a number of functions. Firstly, the vent tanks 107 vent the ullage of
each of the fuel tanks 106 to atmosphere to enable the ingress of air
required to equalise negative pressure in the fuel tanks as a result of,
for example, fuel being burned by the engines 104 or a decrease in
altitude of the aircraft 101. Secondly, the vent tanks 107 vent the
ullage of each of the fuel tanks 106 to atmosphere to enable the egress
of positive pressure of air, fuel vapour or inerting gasses from the
tanks as a result, for example, of an increase in ambient temperature or
altitude of the aircraft 101. Thirdly, the vent tanks 107 are arranged to
vent excess liquid fuel from the fuel tanks 106 to atmosphere as a result
of, for example, exceptional manoeuvres of the aircraft 101 or by
overfilling of the fuel tanks 106 during a refuelling process.

[0017]With reference to FIG. 2, in the present embodiment two fuel tanks
106 and the vent tank 107 are provided by the internal structure of each
of the wings 102. The fuel tanks 106 are arranged with a ventilation
system comprising a first set of conduits 201 for venting the ullage of
each respective fuel tank 106 into the vent tank 107. The fuel and vent
tanks 106, 107 are further provided with a fuel return system comprising
a second set of conduits 202 controlled by pumps 203 having non-return
valves that enable the controlled return of fuel from the vent tank 107
to the fuel tanks 106.

[0018]The vent tank 107 further comprises a vent pipe 204 arranged to
provide fluid communication between the interior of the vent tank 107 and
atmosphere via an ullage vent 205 positioned in the lower wall of the
ullage tank 107 and the aircraft wing 102. In the present embodiment, the
vent pipe 204 is cylindrical and arranged vertically within the vent tank
107 when the aircraft 101 is level. The vent pipe 204 has its lower open
end in direct fluid communication with the ullage vent 205. In the
present embodiment, the position of the upper open end 206 of the vent
pipe 204 defines the maximum designed liquid fuel level 207 of the vent
tank 107. The space in the vent tank 107 above the maximum designed fuel
level 207 is the minimal ullage 208. In the present embodiment, the upper
end 206 of the vent pipe 204 is provided with a lip 209.

[0019]The vent pipe 204 further comprises a flame barrier means 210
arranged to prevent an external flame front from entering the vent tank
107 via the ullage vent 205 and the vent pipe 204. In the present
embodiment, the flame barrier means 210 is operable between two positions
or states 211, 212. In the first position 211, as shown in FIG. 2, the
flame barrier means 210 is in a closed state, that is, the flame barrier
means 210 is arranged as a barrier to flame fronts entering the vent tank
107 via said vent pipe 204. In the second position 212, as indicated by a
broken outline in FIG. 2, the flame barrier means 210 is in an open
state, that is, the flame barrier means 210 is arranged so as to enable
fluid flow between the ullage 208 and the ullage vent means 205 to
circumvent or bypass the flame barrier means 210. In the present
embodiment, the flame barrier means 210 is arranged so as to be only
operable to the open state 212 when an additional external flame barrier
means (not shown in FIG. 2) is connected to the ullage vent 205 as
described in further detail below.

[0020]Thus, the vent tanks 107 are arranged for use in two modes. The
first mode is provided for venting of the vent tanks 107 when no external
flame arrestor is in place. In this first mode, the flame barrier means
210 is in its closed state 211 and all venting of the vent tank 107 is
provided via the vent pipe 204, flame barrier means 210 and the ullage
vent 205. The second mode is provided for venting of the vent tanks 107
during a refuelling process with an external flame arrestor. In this
second mode, with reference to FIG. 3, an external flame barrier means
301 is coupled to the ullage vent 205 and the flame barrier means 210 is
placed in its open state 212 as shown in FIG. 3. The coupling between the
ullage vent 205 and the external flame barrier means 301 is provided by
male coupling means 302 formed on the external flame barrier means 301
and complimentary female coupling means 303 formed in the ullage vent 205
and provides a fluid seal between the coupled parts.

[0021]The external flame barrier means 301 further comprises a hollow
substantially cylindrical body member 304 having a first and second open
ends 305, 306. The first open end 305 is arranged to conform to the
ullage vent 205 and carries the male coupling means 302 in the from a
male part of a bayonet coupling. The ullage vent 205 provides the
complimentary female part of the bayonet coupling. The second open end
306 is open to atmosphere. The external flame barrier means 301 further
comprises a flame barrier element 307 fixed within the body member 304.
The flame barrier element is arranged to provide a flame barrier for
preventing ingress, via the external flame barrier means 301, of a flame
front (FF) external to the vent tank 107 while allowing egress (F) of
fuel, fuel vapour or other liquids or gasses to atmosphere.

[0022]In the present embodiment, the flame barrier means 210 and flame
barrier element 307 are formed from a conventional flame barrier material
such as layered wire mesh. As will be understood by those in the art, the
flame barrier may be formed from any suitable material such as non-woven
meshes or may comprise one or more granular or particulate layers.

[0023]In the present embodiment, the flame barrier means 210 is provided
with a set of circumferential seals 308 located around the flame barrier
means 210 so as to provide a seal between the flame barrier means 210 and
the interior surface of the vent pipe 204 when the flame barrier means
210 is in the closed state 211. In addition, the interior wall of the
vent pipe 204 is provided with a seat 309 for the flame barrier means 210
in its closed state 211. The seat 309 is arranged so as to provide
positive location of the flame barrier means 210 in its closed position
211. The flame barrier means 210 is fixedly mounted within the vent pipe
204 on a drive shaft 310 positioned perpendicular to the central axis of
the vent pipe 204. The drive shaft 310 is rotatably, sealingly mounted in
the wall of the vent pipe 204.

[0024]In the present embodiment, one end of the drive shaft 310 is coupled
to an actuator 311 mounted adjacent the vent pipe 204. The actuator 311
is arranged to drive the drive shaft 310 so as to move the flame barrier
means 210 between its open and closed states 212, 211. The actuator 311
is connected to a controller 312 and a two clusters of sensors and locks
313, 314. The controller 312 controls the operation of the actuator 311,
taking into account inputs from the sensors and locks 313, 314. The first
sensor and lock cluster 313 is positioned adjacent the female coupling
means 303 formed in the ullage vent 205. The first sensor and lock
cluster 313 is arranged to detect whether or not an external flame
barrier means 301 is engaged with the ullage vent 205 and to provide this
data to the controller 312. The first sensor and lock cluster 313 is
further arranged, under the control of the controller 312, to lock an
engaged external flame barrier means 301 within the coupling means 302,
303. The second sensor and lock cluster 314 is positioned adjacent the
seat 308 and arranged to detect whether or not the flame barrier means
210 is seated in the seat 308 in its closed state 211. The first sensor
and lock cluster 313 is further arranged, under the control of the
controller 312, to lock the flame barrier means 210 in its closed state
211. In addition to communications means, in the form of wiring, with the
actuator 311 and sensor/lock clusters 313, 314, the controller 312
further comprises a communications link with the aircraft control systems
(ACS) for communicating data such as fault data or state data from the
sensor/lock clusters 313, 314 and for providing external control or
override facilities.

[0025]In the present embodiment, the controller 312 comprises a
programmable electronic device programmed so as to perform the relevant
functions. The processing performed by the controller 312 when operating
the flame barrier means 210 between its closed and open states 211, 212
will now be described in further detail with reference to the flow chart
of FIG. 4. At step 401, processing is initiated on start-up of the
aircraft systems and moves to step 402. At step 402, input from the first
sensor/lock cluster 313 is awaited that indicates that an external flame
barrier (EFB) means 301 is engaged in the ullage vent 205. Once such
input is received processing moves to step 403. At step 403, the lock is
activated in the first sensor/lock cluster 313 so as to lock the external
flame barrier (EFB) means 301 in the ullage vent 205 and processing moves
to step 404. At step 404 the lock in the second sensor/lock cluster 314
is deactivated to enable movement of the flame barrier means 210 from the
closed position 211 and processing moves to step 405. At step 405, the
actuator 311 is operated so as to move the flame barrier means 210 from
its closed state 211 to its open state 212 and processing moves to step
406.

[0026]At step 406, input from the first sensor/lock cluster 313 is awaited
indicating disengagement of the external flame barrier means 301 and once
received processing moves to step 407. At step 407, the actuator 311 is
operated so as to move the flame barrier means 210 from its open state
212 to its closed state 211 and processing moves to step 408. At step
408, input from the second sensor/lock cluster 314 is awaited indicating
that the flame barrier means 210 is in its closed state 211 and once
received processing moves to step 409. At step 409, the lock of the
second sensor/lock cluster 314 is activated to lock the flame barrier
means 210 is in its closed state 211 and processing moves to step 410. At
step 410, the lock of the first sensor/lock cluster 313 is deactivated to
as to enable full disengagement of the external flame barrier means 301
from the ullage vent 205. Processing then returns to step 402 and
proceeds as described above.

[0027]As will be understood by those skilled in the art, coupling between
the ullage vent 205 and the external flame barrier means 301 is arranged
to maintain its fluid seal between the coupled parts while fully coupled
and during at least the initial stage of the uncoupling movement until
the further uncoupling of the external flame barrier means 301 is stopped
by the first lock 313. This enables the disengagement of the external
flame barrier means 301 to be detected and the flame barrier means 210 to
be moved to its closed position 211 prior to the fluid seal being broken
and the external flame barrier means 301 being fully disengaged from the
ullage vent 205.

[0028]In another embodiment, with reference to FIG. 5, a recess 501 is
provided in the wall of the vent pipe 204. The recess is proportioned so
as to enable the flame barrier means 210 to fit substantially within it
in its open state 212. In the present embodiment, the shaft 310 is
arranged to one side of the vent pipe 204 so that the flame barrier means
210 is arranged to rotate upwardly about its edge from its closed
position 211 abutting the seat 308, into its open position 212
substantially within the recess 501. The vent pipe 204 is also provided
with a widened portion 502 to accommodate the movement of the
substantially disc-shaped flame barrier means 210 between its open and
closed states 212, 211.

[0029]In a further embodiment, with reference to FIG. 6, the flame barrier
means 210 is arranged to be lifted manually from its closed state 211
into its open state 212 by the engagement of an external flame barrier
means 601. In its closed position 211, the flame barrier means 210 is
sealingly located in its seat 308. In its open position 212, the flame
barrier means 210 is lifted by the external flame barrier means 601 into
a widened portion 602 of the vent pipe 204 which provides a conduit for
fluid flow around the flame barrier means 210. In the present embodiment,
the external flame barrier means 601 comprises an extended cylindrical
neck 603 between the male coupling means 302 on its upper open end 305
and the body member 304. The upper end of the cylindrical neck 603 is
provided with a plurality of ports 604 that provide fluid communication F
between the exterior and interior of the external flame barrier means
601.

[0030]In the present embodiment, the ullage vent 207 is provided with a
seal 605 in its interior surface. The seal 605 is arranged to provide a
fluid seal between the ullage vent 207 and the neck 603 during insertion
of the external flame barrier means 601. Furthermore, the extent of the
ports 604 in the direction of insertion of the external flame barrier
means 601 is limited so that when the external flame barrier means 601 is
inserted, the whole of each port 604 moves interior to the seal 605 prior
to the flame barrier means 210 being lifted out of sealing engagement
with its seat 308. In other words, the vertical extent of the ports 604
is limited so as to avoid the risk of providing a path for a flame fronts
to pass into the vent tank 107 during insertion of the external flame
barrier means 601.

[0031]In the present embodiment, the upper end of the external flame
barrier means 601 and the underside of the flame barrier means 210
comprise complimentary elements of a coupling means (not show). Coupling
of the flame barrier means 210, 601 is detected by the sensor of the
first sensor/lock cluster 311. Such detection results in the deactivation
of the corresponding lock of the second sensor/lock cluster 311 that is
operable to lock the flame barrier means 210 in its closed state 211. The
external flame barrier means 601 is then operable to move upwardly so as
to lift the attached flame barrier means 210 into its open state 212 at
which point the lock of the first sensor/lock cluster 311 locks the
external flame barrier means 601 into its fully engaged position. The
removal process for the external flame barrier means 601 is the reverse
of the insertion procedure. The removal procedure is initiated by the
manual release of the lock of the first sensor/lock cluster 311 and
results in the flame barrier element 210 being retuned and locked into
its closed position 211.

[0032]As will be understood by those skilled in the art, the powered or
mechanical elements of the embodiments described above may be wholly or
partially substituted for any other mechanical or powered mechanism for
providing the same function. Actuation may be provided by any suitable
combination of suitable methods such as manual, electric hydraulic power.
The mechanism may be arranged for control either partially or fully
automatically or may be partially or fully manually controlled by ground
or onboard personnel. As will be understood by those skilled in the art,
the sensors and locks may be provided as separate elements. The
arrangement of sensors and locks provided may be varied to suit a given
powering, actuation or control variation as described above.

[0033]As will be understood by those skilled in the art, in any of the
embodiments described herein, an intermediate conduit such as a hose or
pipe may be provided between the ullage vent and the external flame
barrier means so as to conduct any liquid fuel flowing from the ullage
vent away from the aircraft structure. As will be understood by those
skilled in the art, the hatch for the ullage vent may be provided with
further locking or retaining means to prevent accidental or unauthorised
opening.

[0034]The external flame barrier means in combination with the ullage vent
and vent pipe may be arranged so as to provide comparable or greater
fluid flow than a given refuelling means/pump. This arrangement will
reduce the risk of the refuelling pump increasing the pressure within the
fuel tank system beyond its structural limits and thus avoid damage to
the aircraft structure. The external flame barrier means may be arranged
for use during high rate refueling, whereas during lower pressure or
standard refueling operations only the internal flame barrier means may
be utilized.

[0035]As will be understood by those skilled in the art, the coupling
means between the external flame barrier means and the ullage vent may be
provided by any suitable coupling means such as correspondingly threaded
male and female members, push or snap-fit connectors or any other
coupling means suitable for carrying fuel.

[0036]As will be understood by those skilled in the art, the ullage vent
may be provided with an ice screen.

[0037]As will be understood by those in the art, any surface of one or
more of the flame barrier elements may be corrugated or be formed with a
convoluted cross section. Such corrugations or convolutions may run in
any suitable direction through the flame barrier elements. For example,
the corrugations or convolutions may run radially or circumferentially
relative to the central axis of the corresponding external flame barrier
means.

[0038]As will be understood by those in the art, the ullage vent may be
fed by or feed into an aerodynamic duct, such as a NACA (National
Advisory Committee for Aeronautics) duct or the like, for providing an
aerodynamic interface between the ullage vent and the external surface of
the aircraft.

[0039]Embodiments of the invention may enable the vent pipe and flame
barrier arrangements to be more compact since the vent pipe need only be
capable of the relatively low flow rates required when the aircraft is
operating in modes other than the refuelling mode.

[0040]While the present invention has been illustrated by the description
of the embodiments thereof, and while the embodiments have been described
in considerable detail, it is not the intention of the applicant to
restrict or in any way limit the scope of the appended claims to such
detail. Additional advantages and modifications will readily appear to
those skilled in the art. Therefore, the invention in its broader aspects
is not limited to the specific details representative apparatus and
method, and illustrative examples shown and described. Accordingly,
departures may be made from such details without departure from the
applicant's general inventive concept.